PLATE 18 



EXPLANATION OF FIGURES 



Fig. 23 Photomicrograph of a transverse section taken through the subocular 

 lymph sacs (1) of a fifteen-day steelhead trout embryo. P. E. C. 726, slide 1, 

 section 78; injected embryo. 



Fig. 24 Photomicrograph of a transverse section taken through the subocular 

 lymph sacs (/) of a sixteen-day rainbow trout embryo at the level of the infra- 

 orbital veins (#3); showing that the veins are fully injected and that none of the 

 injecta has passed into the sacs. P. E. C. 751, slide 1, section 66. - 



REFERENCES 



1, Subocular lymph sac 22, Carotid artery 



6, Precardinal or jugular vein 23, Infraorbital vein 



15, Hyoidean artery 28, Infundibulum 



20, Caudal end of eye 



110 



